test: simplify helper tests

Author: lukengda

test/src/helper_test.dart

@@ -4,31 +4,26 @@ import 'package:introduction_screen/src/helper.dart';
 void main() {
   // Global variables
   final originalList = [1, 2, 3, 4, 5];
-  final list = ['a', 'b', 'c'];
 
   group('CustomList', () {
-    test('asReversed returns reversed list when isReverse is true', () {
-      final reversedList = originalList.asReversed(true);
-
-      expect(reversedList, [5, 4, 3, 2, 1]);
+    test('asReversed() reverses list when isReverse is true', () {
+      expect(originalList.asReversed(true), [5, 4, 3, 2, 1]);
     });
 
-    test('asReversed returns original list when isReverse is false', () {
-      final originalCopy = originalList.asReversed(false);
-
-      expect(originalCopy, originalList);
+    test('asReversed() returns original list when isReverse is false', () {
+      expect(originalList.asReversed(false), [1, 2, 3, 4, 5]);
     });
 
     test('elementAtOrNull returns the correct element for valid index', () {
-      expect(list.elementAtOrNull(1), 'b');
+      expect(originalList.elementAtOrNull(1), 2);
     });
 
     test('elementAtOrNull returns null for out of bounds index', () {
-      expect(list.elementAtOrNull(5), isNull);
+      expect(originalList.elementAtOrNull(5), isNull);
     });
 
     test('elementAtOrNull returns null for negative index', () {
-      expect(list.elementAtOrNull(-1), isNull);
+      expect(originalList.elementAtOrNull(-1), isNull);
     });
   });
 }